The Alaska Volcano Observatory is raising the Aviation Color Code to ORANGE and Alert Level to WATCH at Shishaldin Volcano. Elevated surface temperatures were detected in satellite data beginning on March 18 and have persisted to the present time. Analysis of this data shows that temperatures are consistent with the eruption of lava within the summit crater. The current activity appears to be confined to the deep summit crater and there have been no observations of lava on the flanks of the volcano or surrounding the summit crater. Web camera images, satellite data and pilot observations over the past week show only minor steam emissions from the mountain's summit crater. There has been no evidence of ash emission.

Sound waves coupling into the ground (ground-coupled air waves) indicative of small explosions in the crater began to be seen in seismic data on March 18 and continue to be detected intermittently.

(12) Volcanic cloud height:

Unknown

(13) Other volcanic cloud information:

Unknown

(14) Remarks:

Shishaldin volcano, located near the center of Unimak Island in the eastern Aleutian Islands, is a spectacular symmetric cone with a base diameter of approximately 10 miles (16 km). A small summit crater typically emits a noticeable steam plume with occasional small amounts of ash. Shishaldin is one of the most active volcanoes in the Aleutian volcanic arc, with at least 54 episodes of unrest including at least 24 confirmed eruptions since 1775. Most of Shishaldin's eruptions have consisted of small ash and steam plumes, although a recent eruption in April-May 1999 produced an ash column that reached a height of 45,000 ft above sea level.

Volcanic Activity Summary:The Alaska Volcano Observatory is raising the Aviation Color Code to ORANGE and Alert Level to WATCH at Shishaldin Volcano. Elevated surface temperatures were detected in satellite data beginning on March 18 and have persisted to the present time. Analysis of this data shows that temperatures are consistent with the eruption of lava within the summit crater. The current activity appears to be confined to the deep summit crater and there have been no observations of lava on the flanks of the volcano or surrounding the summit crater. Web camera images, satellite data and pilot observations over the past week show only minor steam emissions from the mountain's summit crater. There has been no evidence of ash emission.

Sound waves coupling into the ground (ground-coupled air waves) indicative of small explosions in the crater began to be seen in seismic data on March 18 and continue to be detected intermittently.

Remarks: Shishaldin volcano, located near the center of Unimak Island in the eastern Aleutian Islands, is a spectacular symmetric cone with a base diameter of approximately 10 miles (16 km). A small summit crater typically emits a noticeable steam plume with occasional small amounts of ash. Shishaldin is one of the most active volcanoes in the Aleutian volcanic arc, with at least 54 episodes of unrest including at least 24 confirmed eruptions since 1775. Most of Shishaldin's eruptions have consisted of small ash and steam plumes, although a recent eruption in April-May 1999 produced an ash column that reached a height of 45,000 ft above sea level.